Rotary piston machine

ABSTRACT

A rotary piston machine, with a driving part and a driven part, which are geared together, is proposed, for which these parts  17  and  18  run on a common stationary main axle  8.

BACKGROUND OF THE INVENTION

The invention relates to a rotary test machine. Such a rotary pistonmachine is known (German patent 4241320) as a pump, compressor or motor,for which the ridges of teeth of a rotating driving parts, in order tolimit the working spaces, run on a cycloid surface of an also tootheddriven part, driving the latter. The aforementioned working spaces,which are increased or decreased in size for their work during therotation of the parts, in order to produce the delivery action on amedium, are formed between the teeth of the driving and driven parts.

It has also already been proposed (patent application DE 103 35 939.7 ofAug. 2, 2003) that a portion of the machine housing be mounted in a“floating manner”, in order to be able to equalize gap losses and thelike better by these means. However, such a floating arrangement has thedisadvantage that, at the expense of a decrease in the losses throughthe gap, the danger of imbalances arises. The significance of thisdisadvantage depends on the practical use of the object, the rpm thenactually employed and the pressure aimed for playing an important roll.

SUMMARY OF THE INVENTION

Compared to the foregoing, the inventive rotary piston machine has theadvantage that the invention can be used especially in the deliverysystem of fuel-burning engines, for example, as a pre-delivery pump fordiesel injection installations or as pre-delivery pump or a pressure andsupplying pump of gasoline injection installation. The combination as aunit between the engine housing and the machine housing offers thepossibility of making such a delivery pump or pressure pump small, sincethe electric motor can engage the driving part of the rotors directly,without an additional, expensive mounting. The housing can be connectedin different ways, for example, as a screw connection between two“pots”, which embrace, on the one hand, the pump and, on the other, theelectric motor, or there may be beading between a lid part and a potpart, depending on how this appears to be meaningful for practical useand, above all, for being able to produce advantageously. It is ofdecisive importance for the invention that the parts, which relate tothe electric motor, such as the magnets and the mounting of the rotor,are disposed in the machine housing and that the pump parts, includingthe inflow and outflow device for the medium, are accommodated in themachine housing.

Due to the stationary main axle, a good and especially axially identicalguidance of the rotating parts, namely of the rotor of the electricmotor, of the driving part and of the driven part, is achieved, so thateven if the inner housing were to be mounted in a floating manner, therewould be radial matching. Moreover, such an axle can also serve toaxially tie in the parts and, last but not least, offer advantages forautomatic installation in production on a large scale. The relativelyshort width of the known bearings is broadened by a multiple for thestationary main axle, especially for the rotor of the electric motor, asa result of which the specific radial forces are reduced correspondingto the larger bearing surface to the benefit of the service life of therotary piston machine. The length of the service life, as well as thereliability plays an exceptionally significant role especially when usedas a fuel pump in the vehicles.

It should be pointed out here that the development of a minimum amountof noise is aimed for especially in vehicle construction and when a fueldelivery pump is used in a motor vehicle. The slightest imbalances wouldalready lead to appreciable noise. This makes the problem, on which theinvention is based, even clearer. Due to the use of a continuous,stationary main axle, the development of imbalances is prevented. Theuse of a stationary main axis is also known for fuel delivery pumps of adifferent type (Robert Bosch GmbH).

Admittedly, the claimed bearing bushing has already been proposedearlier. However, it does not belong to the state of the art and playsan appreciable role in connecting the individual distinguishing featuresof claim 1 and their developments.

Such an inventive “electric pump” is not limited in its application to afuel delivery pump and, instead, depending on its size and efficiency,can be used for liquid media or gaseous media. In such a case, however,significantly higher pressures can be produced than in the case of aknown fuel delivery pumps (Robert Bosch GmbH or the like).

In accordance with an advantageous development of the invention, thereis a change in the rotational position of the working spaces to thesuction channel and the pressure channel and, with that, to the workingphase of the working spaces in relation to the suction channel and thepressure channel due to the relative rotation of the bearing bushing ofthe driven part on the main axle. A change in the amount conveyed can beachieved in a simple manner by these means.

According to an additional development of the invention, the bearingbushing is connected with a bottom bearing for the driven part, on whichthe latter is supported on its side averted from the driving part andwhich is also disposed rotatably on the main axle. In this connection,the bearing bushing and the bottom bearing have the same axle, whichrests perpendicularly on the bearing surface, on which the driven partis supported. By rotating this bottom bearing on the main axle withinthe machine housing, the above-mentioned relative adjustment, from thestart of the delivery to the inflow and outflow channels, mentionedabove, is shifted relatively, with the result that the deliveryperformance of the machine is changed.

According to an additional advantageous development of the invention,the rotors run in an inner housing, in which the suction channel, whichis open towards the rotors, and the pressure channel are disposed. Thisinner housing is disposed within the rest of the machine housing so thatit does not rotate and does not float and, in particular, is securedagainst rotating with respect to the bottom bearing. In this connection,the inner housing may be disposed in an additional housing bushing andsecured there, so that it cannot twist. This housing bushing, in turn,may be mounted in the outer machine housing.

In accordance with an additional advantageous development of theinvention, the rotors run in a recess (of the inner housing), which isopen and cylindrical towards the driven side and closed and sphericaltowards the driving side. The driving part is supported at thisspherical surface, whereas the driven part is held in its workingposition on the cylindrical side by the bearing bushing and the bottombearing.

According to an additional, advantageous development of the invention,the driving part has an inner, spherical region, at which the drivenpart is supported with a correspondingly configured front face orsupports the bearing bushing of the driven part. By these means, theinner region of the rotors, close to the main axle, which is lesseffective anyhow, is used as an axial supporting means, so that the moreeffective sections of the rotors, which lie radially further to theoutside, form the working spaces.

According to an additional, advantageous development of the invention,the driven part is loaded axially in the direction of the driving part.

According to a development of the invention, which is advantageous inthis regard, the driven part is put under a load in the direction of thedriving part by the force of a spring. Such a force may be of advantage,particularly in the starting phase of such a pump, in order to achievethe tightness between the working flanks of mutually meshing teethrequired for the delivery.

In accordance with a possible, additional development of the inventionin this regard, the pressure channel of the machine is connected with aspace between the driven part and the housing (bottom bearing) on theside averted from the driving part. By these means, it is achieved that,when the medium in the pressure channel has reached a certain pressure,the driven part is pressed against the driving part in such a manner,that the above-mentioned tightness between the flanks can be achieved bythis pressure.

In accordance with an additional, advantageous development of theinvention, advanced for itself, the transitions at the rotors betweenthe mutually facing spherical supporting surfaces providing axialsupport and the surfaces of the teeth, limiting the working space, arerounded off. By means of such a rounding off, on the one hand, a greatertightness is achieved between the boundaries of the working spaces,leading to an improvement in the effective pressure and delivery actionof such a pump, and, on the other, the processing of pump parts in thesesections of the manufacturing process is simplified, quite apart fromthe fact that the danger of chip formation by the sharp-edged parts isavoided. The radius of such rounded off edges preferably is at least 1mm. Basically this radius is independent of the size of the pump parts.

According to an additional development of the invention, which is,however, also advanced for itself, short-circuit channels orshort-circuit grooves, over which, during the rotation and, inparticular, before the suction or pressure channels are opened up,adjacent working spaces can be connected with one another in order toachieve pressure equalization in the working spaces of changingcapacity, are disposed in the bottom surface of the rotors. During therotation of the driven and driving parts and before the suction channelis opened up, the delivery spaces between the parts change, the assignedflanks of the teeth of the one part sliding over corresponding surfacesof the other part, so that the spaces between the teeth, from which theactual working spaces result, act here as harmful spaces. Anoverpressure would result in the one harmful place and a reducedpressure would result in the adjacent space. Due to the invention, thepressure in the spaces is equalized to the benefit of the efficiency ofthe pump.

Further advantages and advantageous developments of the invention can beinferred from the following description, the drawing and the claims.

An example of the object of the invention is described in greater detailin the following and shown in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the inventive fuel delivery pump in the longitudinalsection corresponding to arrow 1 in FIG. 2,

FIG. 2 shows a longitudinal section through the delivery pumpcorresponding to the line II-II in FIG. 1,

FIG. 3 shows the rotors of the pump, assigned to one another, in alongitudinal section on an enlarged scale, as well as in an explodedrepresentation, and

FIG. 4 shows the inner housing of the pump in a longitudinal section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The fuel delivery pump shown has a rotary piston pump 1 and an electricmotor, which drives this pump 1 and is disposed in a motor housing 3,onto which a housing lid 4 is bolted. In this connection, especially theelectric motor is shown in a highly simplified fashion with a rotor 5and a magnet ring 6, as well as an axial locking part 7 of the motorhousing 3, which is connected with the motor housing 3, to which it issealed. In addition, a stationary axle 8 (main axle) of the rotor 5, aswell as the possible pressure connection 9 for the fuel dischargingpipeline are disposed at this locking part 7. The fuel delivery pump isconstructed as an immersion pump, for which the fuel reaches the pumpover suction ports 10, which are only indicated here, in order to leavethe pump once again then over the pressure connection 9. The fuel,within the motor housing 3, flows around the electric motor 5, 6 here.

The second fixed bearing 11 of the rotor 5 is disposed at the housing ofthe pump 1. The rotor 5 is disposed in an appropriate borehole on thefront face of an inner housing 12 of the rotary piston pump 1. Thisinner housing 12 is disposed on the outside in a housing bushing 13,which once again is sealed from the motor housing 3 and clampedpartially in the latter and partially within the housing lid 4.

As can be inferred particularly from FIG. 4, a recess 14 with acylindrical section 15 and a spherical section 16 is provided in theinner housing 12.

Two pump rotors work in this recess 14, namely a driving part 17 and adriven part 18. The driving part 17 is driven over a positive clutch 20by the rotor 5 of the electric motor 2 and transfers the rotationalmovement of the latter to the driven part 18. Cycloid gearings, whichcan be recognized in FIG. 3 and have working surfaces 19, whichappropriately face one another, are provided on the front faces of thedriving part 17 and the driven part 18. By these means, pump workingspaces 21, as can be seen in FIG. 2, are formed between the workingsurfaces 19 and the inner wall of the recess 14.

On the driven side, the recess 14 is closed off by a bottom bearing 22,which is disposed at an angle to the axis of the recess 14 in order toachieve the necessary conveying angle and which is sealed from thehousing bushing 13 at 23. A journal pin 24 is disposed on this bottombearing 22 perpendicularly to the front face of the bottom bearing 22facing the recess 14. The driven part 18 is mounted over a borehole 25(FIG. 3) on the bottom bearing 22.

The driven part 18 is supported over a spherical surface 29, facing thedriving part 17, at a corresponding spherical recess 30 of the drivingpart 17 (FIG. 3).

It can be seen in FIG. 4 how the delivery process takes place. Fuel issupplied to or removed from the working spaces 21 (FIG. 2) overconveying nodules 31, which are disposed in the walls of the innerhousing 12. On the pressure side, the fuel is then passed to theunderside of the driven part 18, as a result of which this is put underload in the direction of the driving part 17. However, the latterfunctions only when the pump has already generated pressure.

All the distinguishing features, presented here, may be essential to theinvention individually as well as in any combinations with one another.

LIST OF REFERENCE SYMBOLS

-   1 Rotary piston pump-   2 Electric motor-   3 Motor housing-   4 Housing lid-   5 Rotor-   6 Magnet ring-   7 Locking part (axial)-   8 Main axle-   9 Connections-   10 Suction connection-   11 Pressure connection-   12 Inner housing-   13 Housing bushing-   14 Recess-   15 Cylindrical section-   16 Spherical section-   17 Driving part-   18 Driven part-   19 Working surfaces-   20 Positive clutch-   21 Pump working spaces-   22 Bottom bearing-   23 Seal-   24 Journal pin-   25 Blind borehole-   26 Helical spring-   27 Sphere-   28 Blind borehole-   29 Spherical surface-   30 Spherical recess-   31 Delivery nodules

1-13. (canceled)
 14. A rotary piston machine, comprising: at least twooperational rotors mounted for rotation, said operational rotorsincluding a driving part and a driven part, said driving part and saiddriven part each including front face denticulation collectively forminga boundary of working spaces, respective axes of said driving part andsaid driven part being disposed at an axial angle relative to oneanother; a machine housing accommodating said at least two operationalrotors; a pressure conduit and a suction conduit intermittentlyconnectable with said working spaces when said operational rotors arerunning; a motor housing and an electric motor housed in said motorhousing, said electric motor including a drive rotor mounted in axialalignment with said driving part, said motor housing and said machinehousing being interconnected; said electric motor and said operationalrotors running on a stationary main axle disposed jointly in said motorhousing and said machine housing; and a bearing bushing rotatablysupporting said driven part and being disposed approximately at saidaxial angle with respect to said driving part.
 15. A rotary pistonmachine according to claim 14, wherein a rotational position of saidworking spaces is alterable relative to said suction and pressureconduits by a rotation of said bearing bushing relative to said drivenpart, thereby permitting adjustment of a working phase of the workingspaces in relation to the suction and pressure conduits.
 16. A rotarypiston machine according to claim 14, further comprising a bottombearing rotatably mounded on the main axle and oriented to support aside of driven part distant from the driving part, said bearing bushingbeing connected with said bottom bearing.
 17. A rotary piston machineaccording to claim 14, further comprising an inner housing accommodatingsaid operational rotors, said pressure conduit and said suction conduitbeing open to said in a direction of said operational rotors anddisposed in said inner housing.
 18. A rotary piston machine according toclaim 17, further comprising a housing bushing in which said innerhousing is non-rotationally disposed.
 19. A rotary piston machineaccording to claim 14, wherein said inner housing includes a recesswhich is open in a direction of the driven part and which is constructedcylindrically and spherically in another direction of the driving part.20. A rotary piston machine according to claim 14, wherein said drivingpart includes an inner spherical region having an appropriatelyconfigured front surface on which at least one of the driven part andthe bearing bushing of the driven part is supportable.
 21. A rotarypiston machine according to claim 14, wherein said driven part issubjectable to axial load in the direction of the driving part.
 22. Arotary piston machine according to claim 20, further comprising aspring, said driven part being subjected to said axial load in thedirection of the driving part by a biasing force of said spring.
 23. Arotary piston machine according to claim 16, wherein the pressureconduit is connected on a side thereof averted from the driving partwith a space between the driven part and the bottom bearing.
 24. Arotary piston machine according to claim 14, wherein: working surfacesdriving part and the driven part comprise indentations; and transitionsbetween spherical supporting surfaces of the driving part and the drivenpart, and surfaces of the indentations, including rounding.
 25. A rotarypiston machine according to claim 24, wherein said rounding has a radiusof at least 1 mm.
 26. A rotary piston machine according to claim 14,wherein said operational rotors include short circuit conduits formed ina lower surface thereof, via which adjacent working spaces areconnectable with one another to achieve pressure equalization forchanging capacities of the working spaces.
 27. A rotary piston machineaccording to claim 26, wherein said adjacent working spaces areconnectable when one of the suction conduit and the pressure conduit isopened.